Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 311810 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 210 PM EDT THU JUL 31 2014 .SYNOPSIS... COOL HIGH PRESSURE WILL PERSIST ONE MORE DAY ACROSS THE AREA TODAY. A COASTAL TROUGH WILL LIFT NORTH ON FRIDAY...AND STALL OVER THE AREA DURING THE WEEKEND. THIS WILL BRING GOOD RAIN CHANCES...WITH PERIODS OF HEAVY RAINFALL POSSIBLE...FRIDAY THROUGH MONDAY. MORE SEASONABLE WEATHER WILL DEVELOP THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 130 PM THURSDAY...LATEST RADAR IMAGERY DEPICTS A FEW SHOWERS BEGINNING TO POP UP ACROSS PORTIONS OF OUR AREA...WITH COVERAGE INCREASING SOUTH AND WEST OF OUR AREA AS WELL. EXPECT THIS GRADUAL TREND OF ISOLATED TO SCATTERED SHOWERS ACROSS OUR AREA TO CONTINUE THROUGH THE REST OF TODAY AND THROUGH THE OVERNIGHT HOURS AS ISENTROPIC LIFT INCREASES ACROSS THE AREA WITH PRECIPITABLE WATER VALUES AROUND 1.6 TO 1.7 INCHES. WOULD NOT ENTIRELY RULE OUT AN ISOLATED THUNDERSTORM...HOWEVER...MID-LEVELS REMAIN FAIRLY DRY THUS WIDESPREAD COVERAGE OF ANY CONVECTION HAS A LOW PROBABILITY. IN ADDITION...WE WILL SEE THE CONTINUATION OF INCREASING CLOUD COVER THIS AFTERNOON WITH TEMPERATURES IN THE LOW TO MID 80S AS SFC HIGH REMAINS IN PLACE THROUGH TONIGHT. GIVEN CLOUD COVER ALREADY IN PLACE...WITH THE EXCEPTION OF AN ADDED DEGREE HERE OR THERE OVER THE NEXT FEW HOURS...OVERALL ARE CLOSE TO...IF NOT AT ALREADY...OUR HIGHS FOR TODAY. AS A FEW WEAK DISTURBANCES CONTINUE TO PROPAGATE AROUND THE UNSEASONABLY DIGGING LONGWAVE TROUGH IN PLACE ACROSS THE EASTERN HALF OF THE US TODAY...A SYNOPTIC TRANSITION WILL CONTINUE TO TAKE ITS COURSE WELL INTO THE OVERNIGHT HOURS. FOCUS TURNS TO THE SFC FRONTAL BOUNDARY STALLED OFFSHORE...WHICH WILL RETROGRADE BACK TOWARDS THE CAROLINA COAST AS A WARM FRONT BY MORNING. WHILE TIME-HEIGHT ANALYSIS CONTINUES TO DEPICT FAIRLY DRY MID-LEVELS...AVAILABLE MOISTURE IN THE UPPER LEVELS SUPPORTS PREVIOUS THINKING THAT CIRRUS CLOUD DECK WILL INCREASE AND PERSIST THROUGH THE PERIOD. GIVEN ANTICIPATED CLOUD COVER...HAVE SLIGHTLY TWEAKED OVERNIGHT LOWS...BUT CONTINUING OVERALL WITH AROUND 70 DEGREES. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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AS OF 330 AM THURSDAY...THE BEGINNING OF AN UNSETTLED...POSSIBLY EXCEEDINGLY WET...PERIOD BEGINS FRIDAY. SEVERAL FEATURES WORK TOGETHER TO MAKE THE SHORT TERM COOL AND WET...AS THE LARGE UPPER TROUGH WHICH HAS BEEN PLAGUING THE AREA THE LAST WEEK OR SO WILL BEGIN TO WEAKEN. THIS TROUGH BEGINS TO ERODE THANKS TO THE PARENT VORTEX FILLING AND LIFTING OFF TO THE NORTHEAST INTO EASTERN CANADA...AND THE STRONG RIDGE ACROSS THE ATLANTIC BEGINNING TO EXPAND BACK TO THE WEST. THIS DRIVES THE TROUGH AXIS WEST OF THE AREA AND CAUSES MID-LEVEL FLOW TO BECOME INCREASINGLY SOUTHERLY...A DIRECTION WHICH MOISTENS THE ATMOSPHERIC COLUMN. AT THE SURFACE...THE COLD FRONT WHICH HAS BEEN STALLED OFFSHORE SINCE TUESDAY...WILL LIFT BACK AS A TROUGH/WARM FRONT FRIDAY BEFORE STALLING OVER THE AREA ON SATURDAY...FURTHER ENHANCING MOIST ADVECTION IN THE LOWER LEVELS OF THE COLUMN...AND PWATS CLIMB ABOVE 2 INCHES FRIDAY NIGHT AND REMAIN THERE ON SATURDAY. ALL OF THIS TOGETHER SUGGESTS INCREASINGLY UNSETTLED WEATHER DURING THE SHORT TERM...WITH WIDESPREAD SHOWERS AND THUNDERSTORMS LIKELY. WITH PWATS ABOVE TWO INCHES...SURFACE CONVERGENCE ALONG THE FRONT...AND 300MB DIFFLUENCE WITHIN A NEARLY STATIONARY JET STREAK ON DOWNWIND SIDE OF THE UPPER TROUGH...PERIODS OF HEAVY RAIN ARE LIKELY WITHIN CONVECTION DURING THE PERIOD. WPC IS HIGHLIGHTING THE AREA FOR 1-3" OF QPF...AND THIS LOOKS MORE THAN REASONABLE FOR THE TIMEFRAME. WILL BUMP POP TO LIKELY FRI AND SAT...WITH NO TIME PERIOD FAVORED SPECIFICALLY FOR THE HEAVIEST AND MOST WIDESPREAD RAINFALL. DUE TO CLOUDS AND THE CONTINUED UPPER TROUGH...TEMPS THROUGH THE PERIOD WILL REMAIN BELOW NORMAL...TO WELL BELOW NORMAL...FOR HIGHS. LOW TO MID 80S EXPECTED FRIDAY...WITH HIGHS ONLY SLIGHTLY ABOVE 80 ON SATURDAY. LOWS FRIDAY NIGHT AROUND 70 WILL RISE A FEW DEGREES INTO THE LOW 70S FOR SATURDAY NIGHT.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 330 AM THURSDAY...VERY UNSETTLED THE FIRST HALF OF THE PERIOD...BUT A SLOW RETURN TO MORE TYPICALLY SUMMERTIME CAROLINAS WEATHER IS EXPECTED BY THE MIDDLE OF NEXT WEEK. LARGE UPPER TROUGH WILL VERY SLOWLY DAMPEN THROUGH THE EXTENDED WHILE 5H RIDGE RETROGRADES TO WEST AND BECOMES CENTERED OFF THE SE COAST LATE IN THE EXTENDED. AT THE SURFACE...A COASTAL TROUGH STALLED IN THE VICINITY WILL SERVE AS A FOCUS FOR CONVECTION SUN/MON...WHICH COMBINES WITH PWATS OVER 2 INCHES...AND STRONG DIFFLUENCE ALOFT...TO PRODUCE AN EXTENDED PERIOD OF WIDESPREAD SHOWERS/STORMS WITH HEAVY RAINFALL. WPC GRAPHICS SUGGESTS 2-4" OF QPF SUN-TUE...AND WILL CARRY LIKELY POP SUNDAY...HIGH CHC ON MONDAY. SLOW IMPROVEMENT OCCURS THEREAFTER AS THE TROUGH MORE QUICKLY ERODES TO THE NORTH AND THE SURFACE BOUNDARY WASHES OUT...BUT TUESDAY WILL LIKELY FEATURE AGAIN HIGHER-THAN-CLIMO POP...BEFORE IMPROVEMENT OCCURS WEDNESDAY. A WARMING TREND WILL OCCUR THROUGH THE EXTENDED...BUT MUCH OF THE PERIOD WILL REMAIN BELOW NORMAL...WITH SEASONABLE TEMPS DEVELOPING ONLY BY MID-WEEK. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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AS OF 18Z...VFR CONDITIONS FOR THE REST OF TODAY MAY DETERIORATE TO MVFR OVERNIGHT AS RAIN CHANCES INCREASE ACROSS OUR AREA. WILL MAINTAIN BKN CIGS THIS AFTN AS CLOUD COVER ASSOCIATED WITH THE UPPER TROUGH CONTINUES TO STREAM OVERHEAD. EAST WINDS HAVE PICKED UP MORE THAN EXPECTED...SO HAVE ADDED PREVAILING WINDS AROUND 10 KTS WITH HIGHER GUSTS AT THE COASTAL TERMS. RAIN CHANCES INLAND INCREASE THIS EVENING AS WEAK UPPER DISTURBANCES ROTATE AROUND THE TROUGH...SO WILL MAINTAIN VCSH FOR KFLO/KLBT AFTER 00Z FRI. AS THE STALLED FRONT OFFSHORE LIFTS BACK NORTHWARD AS A WARM FRONT OVERNIGHT...SHOWERS MAY ENCROACH UPON THE COASTAL SITES AFTER 06Z FRI. BY 12Z THE FRONT SHOULD BE DRAPED OVER OUR CWA WITH -SHRA AT ALL TAF SITES. WINDS WILL SHIFT TO THE SOUTHEAST BEHIND THE FRONT. DEPENDING ON HOW PERSISTENT AND HOW EARLY THE RAINFALL BEGINS...MVFR CIGS COULD DEVELOP OVERNIGHT OR HOLD OFF UNTIL EARLY FRI MORNING. THOUGH BRIEF IFR CIGS CANNOT BE RULED OUT...MVFR SHOULD PREVAIL BASED ON THE LATEST GUIDANCE. EXTENDED OUTLOOK...SHRA/TSRA LIKELY WITH PERIODS OF MVFR CONDITIONS SAT THROUGH MON AS A FRONT STALLS AND FINALLY DISSIPATES OVER THE EASTERN CAROLINAS. CHANCE OF SHOWERS CONTINUES ON TUE.
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